Variation of parameters - i have different particular soluti

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Discussion Overview

The discussion revolves around the variation of parameters method for solving a third-order ordinary differential equation (ODE). Participants explore the implications of rearranging the fundamental solutions in the context of finding particular solutions.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant describes their process of finding a particular solution using the variation of parameters method and questions whether it is normal to obtain different results by changing the arrangement of the fundamental solutions.
  • The same participant wonders if this implies the existence of multiple valid particular solutions based on the arrangement of the fundamental solutions.
  • Another participant asks for clarification on the different answers obtained, suggesting they might be equivalent despite appearing different.
  • A later reply indicates that upon reviewing their work, the original poster discovered an error in their calculations, which led to the same results after correction.
  • A humorous remark is made about trusting senior colleagues, implying a cautionary perspective on relying solely on others' solutions.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of rearranging the fundamental solutions, as the original poster's confusion was clarified through the discovery of an error in their calculations.

Contextual Notes

The discussion highlights the importance of careful verification in mathematical solutions and the potential for errors in calculations that can lead to differing results.

omar yahia
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i was trying to get a particular solution of a 3rd order ODE using the variation of parameters method
the homogeneous solution is yh = c1 e-x + c2 ex + c3 e2x
the particular solution is yp=y1u1+y2u2+y3u3
as u1=∫ (w1 g(x) /w) dx , u2=∫ (w2 g(x) /w) dx , u3=∫ (w3 g(x) /w) dx
w =
|y1 y2 y3|
|y'1 y'2 y'3|
|y''1 y''2 y''3|

when i choose y1 , y2 , y3 to be e-x,ex,e2x i get an answer ,
but when i change the arrangement (like: ex,e-x,e2x )
i get another different answer !

so , i have two questions
1 is it normal to have different results when changing who is y1 , y2 , y3 , or am i doing something wrong?
2 if it is normal , does that mean i can have too many different particular solutions , just by changing who is y1 , y2 , y3?
 
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What are the different answers you get?
Maybe they are equivalent, and just look differently?
 
mfb said:
What are the different answers you get?
Maybe they are equivalent, and just look differently?
:smile:
ummmmmm ... ahhhh .. actually ... when you asked me to show the results i went to prepare them for uploading
and as i was rewriting the solution i discovered an extra (2) multiplied in one little tiny term , will i fixed it and went on , and the results were the same indeed , i am terribly sorry for this mistake it happened because i trusted the solution of a senior without a thorough revision
thank you for your reply :smile: and i apologies again.
 
Never trust a senior!
 

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